Layout for reticle and wafer scanning electron microscope registration or overlay measurements

ABSTRACT

A method and a resulting device are provided for forming stack overlay and registration monitoring structures for FEOL layers including implant layers and for forming BEOL SEM overlay and registration monitoring structures including BEOL interconnections, respectively. Embodiments include forming an active monitoring structure having first and second edges separated by a first distance in an active layer on a semiconductor substrate; forming a poly monitoring structure having first and second edges separated by a second distance in a poly layer; and forming one or more contact monitoring structures in a contact layer, collectively exposing at least the first and second edges of each of the active and poly monitoring structures; wherein the active, poly, and contact monitoring structures are formed in an area which includes no IC patterns in the active, the poly, and the contact layers, respectively.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. application Ser. No.13/835,147, filed Mar. 15, 2013, the content of which is incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to semiconductor devices includinginterconnects that require two-dimensional (2D) registration measurementor overlay reticle measurement. The present disclosure is particularlyapplicable to 45 nanometer (nm) and below technology nodes, but it isalso applicable to all technology nodes.

BACKGROUND

There is a demand for structures that can be evaluated by a criticaldimension scanning electron microscope (CDSEM) (or even atomic forcemicroscopy (AFM) to some extent) on a wafer and still be verified on themask with today's mask metrology. However, this is only possible if thedimensions and the appearance of the structures are compatible withcurrent CDSEM measurement approaches and if the relevant reference layercan be exposed and dimensions of the underlying layer can be assessedduring the measurement of the current layer. Such evaluations areparticularly problematic for interconnects due to limited visibility ofburied layers. Currently, for 45 nm and below technology nodes there aremicro-blossom targets or process control images (PCIs) for reticleregistration measurement. However, micro-blossom targets cannot provide2D registration measurements or provide the wafer CDSEM overlymeasurement and, at the same time, enable monitoring ofinterconnections.

A need therefore exists for methodology enabling 2D registrationmeasurement or overlay reticle measurement and monitoring ofinterconnections and SEM overlay measurements and the devices used forsuch methodology.

SUMMARY

An aspect of the present disclosure is a method of forming stack overlayand registration monitoring structures for front-end-of-line (FEOL)layers including implant layers and a method of forming back-end-of-line(BEOL) SEM overlay and registration monitoring structures including BEOLinterconnections.

Another aspect of the present disclosure is a device including overlayand registration monitoring structures for FEOL layers including implantlayers and a device including BEOL SEM overlay and registrationmonitoring structures.

Additional aspects and other features of the present disclosure will beset forth in the description which follows and in part will be apparentto those having ordinary skill in the art upon examination of thefollowing or may be learned from the practice of the present disclosure.The advantages of the present disclosure may be realized and obtained asparticularly pointed out in the appended claims.

According to the present disclosure, some technical effects may beachieved in part by a method including: forming an active monitoringstructure having first and second edges separated by a first distance inan active layer on a semiconductor substrate; forming a polysilicon(poly) monitoring structure having first and second edges separated by asecond distance in a poly layer; and forming one or more contactmonitoring structures in a contact layer, collectively exposing at leastthe first and second edges of each of the active and poly monitoringstructures; wherein the active, poly, and contact monitoring structuresare formed in an area which includes no integrated circuit (IC) patternsin the active, the poly, and the contact layers, respectively.

Aspects of the present disclosure include the first and second distancesare in different directions; the one or more contact monitoringstructures comprise at least first, second, and third contact monitoringstructures; the first and second contact monitoring structures exposethe first and second edges of the active monitoring structure; and thesecond and third contact monitoring structures expose the first andsecond edges of the poly monitoring structure.

Further aspects include forming a second active monitoring structure inthe active layer on a semiconductor substrate; and forming a second polymonitoring structure in the poly layer, wherein one of the first,second, and third contact monitoring structures exposes one of the firstand second edges of each of the first active and first poly monitoringstructures and exposes a first edge of each of the second active andsecond poly monitoring structures. Additional aspects include forming afourth contact monitoring structure in the contact layer, exposing asecond edge of the second active monitoring structure, opposite thefirst edge; and forming a fifth contact monitoring structure in thecontact layer, exposing a second edge of the second poly monitoringstructure, opposite the first edge. Another aspect includes forming aplurality of implant monitoring structures in an implant layer on thesemiconductor substrate in an area which includes no IC patterns in theimplant layer, wherein a first implant monitoring structure havingfirst, second, third, and fourth edges is formed on top of either theactive monitoring structure or the poly monitoring structure, and thefirst, second, third, and fourth edges are all exposed. An additionalaspect includes the second distance being less than and in the samedirection as the first distance; the active monitoring structure hasthird and fourth edges separated by a third distance in a thirddirection different than the first direction; the poly monitoringstructure has third and fourth edges separated by a fourth distance lessthan and in the same direction as the third distance; and one contactmonitoring structure exposes the first, second, third, and fourth edgesof the active monitoring structure and first, second, third, and fourthedges of the poly monitoring structure

Another aspect of the present disclosure is a device including: asemiconductor substrate; an active layer including an active monitoringstructure having first and second edges separated by a first distance; apoly layer including a poly monitoring structure having first and secondedges separated by a second distance; and a contact layer including oneor more contact monitoring structures, collectively exposing at leastthe first and second edges of each of the active and poly monitoringstructures, wherein the active monitoring structure, the poly monitoringstructure, and the first, second, and third contact monitoringstructures are in an area which includes no IC pattern in the active,the poly, and the contact layers, respectively.

Aspects of the device include the active monitoring structure havingfirst and second edges separated by the first distance in a firstdirection; the poly monitoring structure having first and second edgesseparated by the second distance in a second direction that is differentthan the first direction; the contact layer including at least first,second, and third contact monitoring structures, wherein the first andsecond contact monitoring structures expose the first and second edgesof the active monitoring structure and the second and third contactmonitoring structures expose the first and second edges of the polymonitoring structure. Further aspects include a second active monitoringstructure in the active layer on a semiconductor substrate; and a secondpoly monitoring structure in the poly layer, wherein one of the first,second, and third contact monitoring structures exposes one of the firstand second edges of each of the first active and first poly monitoringstructures and exposes a first edge of each of the second active andsecond poly monitoring structures. Additional aspects include a fourthcontact monitoring structure in the contact layer, exposing a secondedge of the second active monitoring structure, opposite the first edge;and a fifth contact monitoring structure in the contact layer, exposinga second edge of the second poly monitoring structure, opposite thefirst edge Another aspect includes a plurality of implant monitoringstructures in an implant layer on the semiconductor substrate in an areawhich includes no IC patterns in the implant layer, wherein a firstimplant monitoring structure having first, second, third, and fourthedges is formed on top of either the active monitoring structure or thepoly monitoring structure and the first, second, third, and fourth edgesare all exposed. An additional aspect includes the active, poly, andcontact monitoring structures having one or more convex polygonalshapes.

An additional aspect of the present disclosure is a method including:forming an initial metal monitoring structure having a first portionhaving first and second edges separated by a first distance in a firstdirection, the initial metal monitoring structure being formed in aninitial metal layer of a semiconductor substrate; forming a subsequentmetal monitoring structure having a first portion having first andsecond edges separated by a second distance in the first direction, thesubsequent metal monitoring structure being formed in a subsequent metallayer adjoining the initial metal layer; and forming a via within thefirst portion of the subsequent metal monitoring structure, the viaexposing the first and second edges of the first portion of the initialmetal monitoring structure, wherein the initial and the subsequentmonitoring structures are formed in an area which includes no integratedIC patterns in the initial metal layer and the subsequent metal layer,respectively

Aspects of the present disclosure include forming each of the initialmetal monitoring structure and the subsequent metal monitoring structurehaving a second portion, wherein the a part of the second portion of thesubsequent metal monitoring structure overlays a part of the secondportion of the initial metal monitoring structure. Further aspectsinclude the first and second portions of the initial metal monitoringstructure extending perpendicularly to the first and second portions ofthe subsequent metal monitoring structure, respectively. Additionalaspects include forming each of the initial and the subsequent metalmonitoring structures in a cross shape by: forming the initial metalmonitoring structure having: a second portion having third and fourthedges separated by a third distance in a second direction, a thirdportion having fifth and sixth edges separated by a fourth distance inthe first direction, and a fourth portion having seventh and eighthedges separated by a fifth distance in the second direction; and formingthe subsequent metal monitoring structure having: a second portionhaving third and fourth edges separated by a sixth distance in thesecond direction, the sixth distance being greater than the thirddistance, a third portion having fifth and sixth edges separated by aseventh distance in the first direction, the seventh distance being lessthan the fourth distance, and a fourth portion having seventh and eighthedges separated by an eighth distance in the second direction, theeighth distance being less than the fifth distance. Another aspectincludes forming a second via within the second portion of thesubsequent metal monitoring structure, exposing the third and fourthedges of the second portion of the initial metal monitoring structure.

A further aspect of the present disclosure is a device including: asemiconductor substrate; an initial metal layer including an initialmetal monitoring structure having a first portion having first andsecond edges separated by a first distance in a first direction; asubsequent metal layer, adjoining the initial metal layer and includinga subsequent metal monitoring structure having a first portion havingfirst and second edges separated by a second distance in the firstdirection; and a via through the subsequent metal monitoring structureand within the first portion of the subsequent metal monitoringstructure, the via exposing the first and second edges of the firstportion of the initial metal monitoring structure, wherein the initialmetal monitoring structure and the subsequent metal monitoring structureare in an area which includes no IC pattern in the one or more initialmetal layers and the one or more subsequent metal layers, respectively

Aspects include the initial metal monitoring structure and thesubsequent monitoring structure having a second portion, wherein a partof the second portion of the subsequent metal monitoring structureoverlays a part of the second portion of the initial metal monitoringstructure. Other aspects include the first and second portions of eachof the initial and subsequent metal monitoring structures extendingperpendicularly to the first and second portions of the subsequent metalmonitoring structure, respectively. Further aspects include wherein eachof the initial and the subsequent metal monitoring structures is formedin a cross shape wherein: the initial metal monitoring structure has: asecond portion having third and fourth edges separated by a thirddistance in a second direction, a third portion having fifth and sixthedges separated by a fourth distance in the first direction, and afourth portion having seventh and eighth edges separated by a fifthdistance in the second direction; and the subsequent metal monitoringstructure has: a second portion having third and fourth edges separatedby a sixth distance in the second direction, the sixth distance beinggreater than the third distance, a third portion having fifth and sixthedges separated by a seventh distance in the first direction, theseventh distance being less than the fourth distance, and a fourthportion having seventh and eighth edges separated by an eighth distancein the second direction, the eighth distance being less than the fifthdistance. Additional aspects include a second via within the secondportion of the subsequent metal monitoring structure, exposing the thirdand fourth edges of the second portion of the initial metal monitoringstructure.

Additional aspects and technical effects of the present disclosure willbecome readily apparent to those skilled in the art from the followingdetailed description wherein embodiments of the present disclosure aredescribed simply by way of illustration of the best mode contemplated tocarry out the present disclosure. As will be realized, the presentdisclosure is capable of other and different embodiments, and itsseveral details are capable of modifications in various obviousrespects, all without departing from the present disclosure.Accordingly, the drawings and description are to be regarded asillustrative in nature, and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is illustrated by way of example, and not by wayof limitation, in the figures of the accompanying drawing and in whichlike reference numerals refer to similar elements and in which:

FIGS. 1A, 2, and 3A schematically illustrate registration/overlay marksfor active, poly, and contact layers, in one direction for FIG. 1A andin two directions for FIGS. 2 and 3A, in accordance with an exemplaryembodiment;

FIGS. 1B, 1C, 1D, 1E, and 3B schematically illustrateregistration/overlay marks for active, poly, contact, and implantlayers, in one and two directions, respectively, in accordance with anexemplary embodiment; and

FIGS. 4 and 5 schematically illustrate registration/overlay marks fortwo consecutive metal layers, in one and two directions, respectively,in accordance with an exemplary embodiment.

DETAILED DESCRIPTION

In the following description, for the purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of exemplary embodiments. It should be apparent, however,that exemplary embodiments may be practiced without these specificdetails or with an equivalent arrangement. In other instances,well-known structures and devices are shown in block diagram form inorder to avoid unnecessarily obscuring exemplary embodiments. Inaddition, unless otherwise indicated, all numbers expressing quantities,ratios, and numerical properties of ingredients, reaction conditions,and so forth used in the specification and claims are to be understoodas being modified in all instances by the term “about.”

The present disclosure addresses and solves the current problem of aninability to evaluate and verify by CDSEM (or AFM) registration andoverlay structures, on a wafer and on a lithographic mask, attendantupon forming and employing the lithographic mask with current maskmetrology. In accordance with embodiments of the present disclosure,overlapping monitoring structures are used for registration and overlaymeasurements.

Methodology in accordance with embodiments of the present disclosureincludes forming an active monitoring structure having first and secondedges separated by a first distance in an active layer on asemiconductor substrate. A poly monitoring structure having first andsecond edges separated by a second distance is formed in a poly layer.One or more contact monitoring structures are formed in a contact layer,collectively exposing at least the first and second edges of each of theactive and poly monitoring structures, wherein the active, poly, andcontact monitoring structures are formed in an area which includes nointegrated circuit (IC) patterns in the active, the poly, and thecontact layers, respectively.

Still other aspects, features, and technical effects will be readilyapparent to those skilled in this art from the following detaileddescription, wherein preferred embodiments are shown and described,simply by way of illustration of the best mode contemplated. Thedisclosure is capable of other and different embodiments, and itsseveral details are capable of modifications in various obviousrespects. Accordingly, the drawings and description are to be regardedas illustrative in nature, and not as restrictive.

Adverting to FIG. 1A, an active monitoring structure 101 having firstand second edges separated by a first distance is formed in an activelayer on a semiconductor substrate, in an area which does not include ICpatterns. A poly monitoring structure 103 having first and second edgesseparated by a second distance is then formed in a poly layer on thesemiconductor substrate, e.g., diagonally aligned with and proximate tothe active monitoring structure 101. Similar to the active monitoringstructure 101, the poly monitor structure 103 is formed in an area whichdoes not include IC patterns. Thereafter, a first contact monitoringstructure 105 is formed in a contact layer on the semiconductorsubstrate exposing one of the first and second edges of the activemonitoring structure 101. A second monitoring structure 107 is formed inthe contact layer exposing a second edge of the active monitoringstructure 101, opposite the first edge, and one of the first or secondedges of the poly monitoring structure 103. Also in the contact layer, athird contact monitoring structure 109 is formed so that the thirdcontact monitoring structure 109 exposes a second edge of the polymonitoring structure 103, opposite the first edge. In general, only theportions of the active monitoring structure 101 and the poly monitoringstructure 103 within the first, second, and third contact monitoringstructures 105, 107, and 109 are visible as depicted by the solid lines.In addition, the first contact monitoring structure 105, the secondcontact monitoring structure 107, and the third contact monitoringstructure 109 are all formed in an area that does not include ICpatterns. More specifically, FIG. 1A shows the SEM registration oroverlay layout for active, poly, and contact layers in one direction.Further, although illustrated as squares, monitoring structures 101through 109 may alternatively be formed as one or more convex polygonalshapes.

For 45 nm technology nodes and beyond, the implant layer to active layerSEM overlay measurement is important for both the reticle and the wafer.A first and a second implant monitoring structure 111 and 113,respectively, each having first, second, third, and fourth edges may beformed in an implant layer on the semiconductor substrate in an areathat does not include IC patterns, as illustrated in FIG. 1B. Moreover,the first and second implant monitoring structures 111 and 113 may beformed overlying and within the active monitoring structure 101 or thepoly monitoring structure 103, respectively, and the first, second,third, and fourth edges are all exposed. Adverting to FIG. 1C, thefirst, second, and third contact monitoring structures 105, 107, and 109may then be formed as in FIG. 1A so that the first implant monitoringstructure 111 is between the first contact monitoring structure 105 andthe second contact monitoring structure 107 and the second implantmonitoring structure 113 is between the second contact monitoringstructure 107 and the third contact monitoring structure 109. Theoverlay measurements for the implant monitoring structures 111 and 113can be obtained in both the X and the Y direction for both reticle andwafer CDSEM.

Alternatively, as illustrated in FIG. 1D, the active monitoringstructure 101 having first and second edges separated by a firstdistance may be formed in the active layer of the semiconductorsubstrate, in an area which does not include IC patterns. The polymonitoring structure 103 having first and second edges separated by asecond distance less than the first distance but in the same directionas the first distance may then be formed in the poly layer on thesemiconductor substrate, over the active monitoring structure, such thatthe first and second edges of the active monitoring structure 101 arenot obscured by the poly monitoring structure 103. In addition, theactive monitoring structure 101 has third and fourth edges separated bya third distance in a second direction different than the firstdistance, and the poly monitoring structure has third and fourth edgesseparated by a fourth distance less than the third distance in thesecond directions, such that the third and fourth edges of the activemonitoring structure are not obscured by the poly monitoring structure.Thereafter, the first contact monitoring structure 105 is formed in acontact layer on the semiconductor substrate, over the poly monitoringstructure. The first contact monitoring element is sized such thatdistances between opposite edges in the first and second directions aregreater than the first and third distances, respectively, betweenopposite edges of the active monitoring structure. Further, the firstcontact monitoring structure 105 is formed such that it exposes thefirst, second, third, and fourth edges of both the active monitoringstructure 101 and the poly monitoring structure 103.

As illustrated in FIG. 1E, the implant monitoring structure 111 havingfirst, second, third, and fourth edges may be formed within theboundaries of the first, second, third, and fourth edges of polymonitoring structure 103 in FIG. 1D. Thereafter, when the first contactmonitoring structure 105 is formed, first, second, third, and fourthedges of the implant monitoring structure 111 are exposed in addition tothe first, second, third, and fourth edges of the active monitoringstructure and the poly monitoring structure. As in FIG. 1D, the activemonitoring structure 101, the poly monitoring structure 103, contactmonitoring structure 105, and the implant monitoring structure 111, areformed in an area which includes no IC patterns in the active, the poly,the implant, and the contact layers, respectively.

Adverting to FIG. 2, a second active monitoring structure 201 may beformed in the same manner as the active monitoring structure 101,instead of the poly monitoring structure 103. In other words, the secondactive monitoring structure 201 may be formed diagonal and proximate tothe active monitoring structure 101. Next, similar to the polymonitoring structure 103, a poly monitoring structure 203 may be formedin the poly layer of the semiconductor substrate in an area that doesnot include IC patterns. In particular, the poly monitoring structure203 may be formed diagonal and proximate to the active monitoringstructure 101 and aligned horizontally with the active monitoringstructure 201. A second poly monitoring structure 205 may be formed inthe same manner as the poly monitoring structure 203, but diagonallyaligned with and proximate to both the poly monitoring structure 203 andthe second active monitoring structure 201. Thereafter, the first,second, and third contact monitoring structures 105, 107, and 109 may beformed as in FIG. 1A. However, the first, second, and third contactmonitoring structures 105, 107, and 109 expose one of the first andsecond edges of the first active and first poly monitoring structures101 and 103, respectively, and expose a first edge of each of the secondactive and second poly monitoring structures 201 and 203, respectively.Again, only portions of the active monitoring structures 101 and 201 andthe poly monitoring structures 203 and 205 within the first, second, andthird contact monitoring structures 105, 107, and 109 are visible asdepicted by the solid lines. Further, although illustrated as squares,monitoring structures 201 through 205 may alternatively be formed as oneor more convex polygonal shapes.

When there is sufficient space in the contact layer, a fourth contactmonitoring structure 301 may be formed in the same manner as the firstcontact monitoring structure 105, as illustrated in FIG. 3A. Morespecifically, the fourth contact monitoring structure 301 exposes asecond edge of the second active monitoring structure 201, opposite thefirst edge. In addition, a fifth contact monitoring structure 303 may beformed in the same manner as the first contact monitoring structure 105,but the fifth contact monitoring structure 303 exposes a second edge ofthe second poly monitoring structure 203, opposite the first edge.Again, although illustrated as squares, monitoring structures 301 and303 may alternatively be formed as one or more convex polygonal shapes.

Adverting to FIG. 3B, a first implant monitoring structure 331 and asecond implant monitoring structure 333 similar to the first and secondimplant monitoring structures 111 and 113 of FIG. 1B may be formed inthe implant layer on the semiconductor substrate in an area that doesnot include IC patterns. In particular, the first and second implantmonitoring structures 331 and 333 may be formed overlying and within theactive monitoring structure 101 and the second active monitoringstructure 201, respectively, so that the first, second, third, andfourth edges of each implant monitoring structures 331 and 333 are allexposed. Thereafter, the first, second, third, fourth, and fifth contactmonitoring structures 105, 107, 109, 301, and 303 are formed as in FIG.3A.

Adverting to FIG. 4, an overlay and registration monitoring structurefor metal interconnect layers is illustrated. An initial metalmonitoring structure 401 having first and second edges separated by afirst distance in a first direction and a second portion, is formed inan initial metal layer of a semiconductor substrate, in an area thatdoes not include IC patterns. A subsequent metal monitoring structure403, also having a first portion having first and second edges separatedby a second distance in the first direction and a second portion, isformed in a subsequent metal layer adjoining the initial metal layer, inan area that does not include IC patterns. More specifically, thesubsequent metal monitoring structure 403 is formed such that a part ofthe second portion of the subsequent metal monitoring structure 403overlays a part of the second portion of the initial metal monitoringstructure 401, and wherein the first and second portions of the initialmetal monitoring structure 401 extend perpendicular to the first andsecond portions of the subsequent metal monitoring structure 403,respectively. Next, a via 405 is formed within the first portion of thesubsequent metal monitoring structure 403, the via 405 exposing thefirst and second edges of the first portion of the initial metalmonitoring structure 401. More specifically, similar to FIG. 1A, onlyportions of the initial metal monitoring structure 401 within theboundaries of the via 405 are visible as depicted by the solid lines.This process flow may be repeated for each two consecutively formedmetal layers on the semiconductor substrate. The structure of FIG. 4enables overlay and registration monitoring in one direction.

Adverting to FIG. 5, a monitoring structure for two directions overlayand registration monitoring of metal interconnect layers is illustrated.An initial metal monitoring structure 501 is formed similar to theinitial metal monitoring structure 401 of FIG. 4, but having a secondportion having third and fourth edges separated by a third distance in asecond direction, a third portion having fifth and sixth edges separatedby a fourth distance in the first direction, and a fourth portion havingseventh and eighth edges separated by a fifth distance in the seconddirection. In particular, the initial metal monitoring structure 501formed in a cross shape is formed in an initial metal layer of asemiconductor substrate, in an area that does not include IC patterns. Asubsequent metal monitoring structure 503 is formed similar to thesubsequent metal monitoring structure 403 of FIG. 4, but having a secondportion having third and fourth edges separated by a sixth distance inthe second direction, the sixth distance being greater than the thirddistance, a third portion having fifth and sixth edges separated by aseventh distance in the first direction, the seventh distance being lessthan the fourth distance, and a fourth portion having seventh and eighthedges separated by an eighth distance in the second direction, theeighth distance being less than the first fifth distance. In particular,the subsequent metal monitoring structure 503 formed in a cross shape isformed in a subsequent metal layer of the semiconductor substrate, in anarea that does not include IC patterns. Thereafter, vias 505 and 507 areformed within the first and second portions of the subsequent metalmonitoring structure 503, exposing the first and second edges of thefirst portion of the initial metal monitoring structure 501 and thethird and fourth edges of the second portion of the initial metalmonitoring structure 501, respectively. Again, as with FIG. 4, only theportions of the initial metal monitoring structure 501 within the vias505 and 507 are visible as depicted by the solid lines. Also, similar toFIG. 4, this process flow may be repeated for each two consecutivelyformed metal layers.

The embodiments of the present disclosure can achieve several technicaleffects including providing structures for 2D registration measurement,overlay reticle measurement, and assessment of the direction of theoverlay. More specifically, the change in overlap of the edges of theregistration and overlay structures can be attributed to a sizing changeor a placement change and adjustments made accordingly. In addition, theoverlay measurement for the implant layer can be easily obtained in boththe X and the Y direction for both reticle and wafer CDSEM. Further,where applicable, the present disclosure enables the monitoring of theBEOL interconnections as well as one or two direction SEM overlaymeasurements. The present disclosure enjoys industrial applicability inany of various types of highly integrated semiconductor devices,particularly for 45 nm technology nodes and beyond.

In the preceding description, the present disclosure is described withreference to specifically exemplary embodiments thereof. It will,however, be evident that various modifications and changes may be madethereto without departing from the broader spirit and scope of thepresent disclosure, as set forth in the claims. The specification anddrawings are, accordingly, to be regarded as illustrative and not asrestrictive. It is understood that the present disclosure is capable ofusing various other combinations and embodiments and is capable of anychanges or modifications within the scope of the inventive concept asexpressed herein.

What is claimed is:
 1. A method comprising: forming an initial metalmonitoring structure having a first portion having first and secondedges separated by a first distance in a first direction, the initialmetal monitoring structure being formed in an initial metal layer of asemiconductor substrate; forming a subsequent metal monitoring structurehaving a first portion having first and second edges separated by asecond distance in the first direction, the subsequent metal monitoringstructure being formed in a subsequent metal layer adjoining the initialmetal layer; and forming one or more vias within the first portion ofthe subsequent metal monitoring structure, the via exposing the firstand second edges of the first portion of the initial metal monitoringstructure, wherein the initial and the subsequent monitoring structuresare formed in an area which includes no integrated circuit (IC) patternsin the initial metal layer and the subsequent metal layer, respectively,the one or more vias comprise at least first, second, and third vias,the first and second vias expose the first and second edges of theinitial metal monitoring structure, and the second and third vias exposethe first and second edges of the subsequent monitoring structure. 2.The method according to claim 1, comprising forming each of the initialmetal monitoring structure and the subsequent metal monitoring structurehaving a second portion, wherein a part of the second portion of thesubsequent metal monitoring structure overlays a part of the secondportion of the initial metal monitoring structure.
 3. The methodaccording to claim 2, wherein the first and second portions of theinitial metal monitoring structure extend perpendicular to the first andsecond portions of the subsequent metal monitoring structure,respectively.
 4. The method according to claim 1, comprising formingeach of the initial and the subsequent metal monitoring structures in across shape by: forming the initial metal monitoring structure having: asecond portion having third and fourth edges separated by a thirddistance in a second direction, a third portion having fifth and sixthedges separated by a fourth distance in the first direction, and afourth portion having seventh and eighth edges separated by a fifthdistance in the second direction; and forming the subsequent metalmonitoring structure having: a second portion having third and fourthedges separated by a sixth distance in the second direction, the sixthdistance being greater than the third distance, a third portion havingfifth and sixth edges separated by a seventh distance in the firstdirection, the seventh distance being less than the fourth distance, anda fourth portion having seventh and eighth edges separated by an eighthdistance in the second direction, the eighth distance being less thanthe fifth distance.
 5. The method according to claim 4, comprisingforming a second via within the second portion of the subsequent metalmonitoring structure, exposing the third and fourth edges of the secondportion of the initial metal monitoring structure.
 6. A devicecomprising: a semiconductor substrate; an initial metal layer includingan initial metal monitoring structure having a first portion havingfirst and second edges separated by a first distance in a firstdirection; a subsequent metal layer, adjoining the initial metal layerand including a subsequent metal monitoring structure having a firstportion having first and second edges separated by a second distance inthe first direction; and a via through the subsequent metal monitoringstructure and within the first portion of the subsequent metalmonitoring structure, the via exposing the first and second edges of thefirst portion of the initial metal monitoring structure, wherein theinitial metal monitoring structure and the subsequent metal monitoringstructure are in an area which includes no IC pattern in the one or moreinitial metal layers and the one or more subsequent metal layers,respectively.
 7. The device according to claim 6, wherein each of theinitial metal monitoring structure and the subsequent monitoringstructure has a second portion, wherein a part of the second portion ofthe subsequent metal monitoring structure overlays a part of the secondportion of the initial metal monitoring structure.
 8. The deviceaccording to claim 7, wherein the first and second portions of theinitial metal monitoring structure extend perpendicular to the first andsecond portions of the subsequent metal monitoring structure,respectively.
 9. The device according to claim 6, wherein each of theinitial and the subsequent metal monitoring structures is formed in across shape wherein: the initial metal monitoring structure has: asecond portion having third and fourth edges separated by a thirddistance in a second direction, a third portion having fifth and sixthedges separated by a fourth distance in the first direction, and afourth portion having seventh and eighth edges separated by a fifthdistance in the second direction; and the subsequent metal monitoringstructure has: a second portion having third and fourth edges separatedby a sixth distance in the second direction, the sixth distance beinggreater than the third distance, a third portion having fifth and sixthedges separated by a seventh distance in the first direction, theseventh distance being less than the fourth distance, and a fourthportion having seventh and eighth edges separated by an eighth distancein the second direction, the eighth distance being less than the fifthdistance.
 10. The device according to claim 9, further comprising asecond via within the second portion of the subsequent metal monitoringstructure, exposing the third and fourth edges of the second portion ofthe initial metal monitoring structure.
 11. A device comprising: asemiconductor substrate; an initial layer including an initial metalmonitoring structure having first and second edges separated by a firstdistance; a subsequent layer including a subsequent metal monitoringstructure having first and second edges separated by a second distance;and a via layer including first, second, and third vias, collectivelyexposing at least the first and second edges of each of the initialmetal monitoring structure and subsequent metal monitoring structures,wherein the initial metal monitoring structure, the subsequent metalmonitoring structure, and the first, second, and third vias are in anarea which includes no IC pattern in the initial, the subsequent, andthe via layers, respectively, and wherein the first and second viasexpose the first and second edges of the initial metal monitoringstructure and the second and third vias expose the first and secondedges of the subsequent metal monitoring structure.
 12. The deviceaccording to claim 11, further comprising: the initial metal monitoringstructure having first and second edges separated by the first distancein a first direction; and the subsequent metal monitoring structurehaving first and second edges separated by the second distance in asecond direction that is different than the first direction.
 13. Thedevice according to claim 11, further comprising: a second initial metalmonitoring structure in the initial layer on a semiconductor substrate;and a second subsequent metal monitoring structure in the subsequentlayer, wherein one of the first, second, and third vias exposes one ofthe first and second edges of each of the first initial metal monitoringstructures and first subsequent metal monitoring structures and exposesa first edge of each of the second initial metal monitoring structuresand second subsequent metal monitoring structures.
 14. The deviceaccording to claim 12, further comprising: a fourth via in the vialayer, exposing a second edge of the second initial metal monitoringstructure, opposite the first edge; and a fifth via in the via layer,exposing a second edge of the second subsequent metal monitoringstructure, opposite the first edge.
 15. The device according to claim11, further comprising: a plurality of implant monitoring structures inan implant layer on the semiconductor substrate in an area whichincludes no IC patterns in the implant layer, wherein a first implantmonitoring structure having first, second, third, and fourth edges isformed on top of either the initial metal monitoring structure or thesubsequent metal monitoring structure and the first, second, third, andfourth edges are all exposed.
 16. The device according to claim 11,wherein the second distance is less than and in the same direction asthe first distance; the initial metal monitoring structure has third andfourth edges separated by a third distance in a third directiondifferent than the first direction; the subsequent metal monitoringstructure has third and fourth edges separated by a fourth distance lessthan and in the same direction as the third distance; and one viaexposes the first, second, third, and fourth edges of the initial metalmonitoring structure and first, second, third, and fourth edges of thesubsequent metal monitoring structure.